Progressive burning firearm propellant



Aug. 13, 1968 H. E. MICHAEL PROGRESSIVE BURNING FIREARM PROPELLANT Filed July 25, 1966 FIG. 3

FIG. 2

DISTANCE TRAVELLEB FIG. 4

PRES lSUR I INVENTOR.

PRESiSURE mvmm FIG.5

United States Patent 3,396,661 PROGRESSIVE BURNENG FIREARM PROPELLANT Harold E. Michael, 30714 Tarapaca Road, Miraleste, Calif. 90732 Filed July 25, 1966, Ser. No. 567,648 2 Claims. (Cl. 102103) ABSTRACT OF THE DISCLOSURE A firearm propellant is provided in the form of a shaped charge made up of a plurality of discs in a stacked coaxial configuration to define a cylindrical shape coaxial with the shell. A central longitudinal bore passes through the stacked discs and a burning inhibitor is provided on portions of at least one of the faces of the various discs in a pattern toleave ignition lines. The exterior of the cylindrical shape defined by the discs include voids, the entire configuration being such that ignition of the charge generate-s propellant gas at a rate proportional to time squared to accelerate the projectile :at a constant rate.

This invention relates to propellants as used in firearms such as revolvers, pistols, rifles, machine guns, and artillery.

In my copending patent application Ser. No. 383,759, filed July 20, 1964, now Patent No. 3,264,997, and entitled Propellant Configurations for Use in Firearms," there are disclosed various propellant configurations for use in firearms which result in an increase in the density of the propellant thereby enabling the size of the cartridge case required for a given weight of propellant to be de creased. As a consequence, certain economies in size and weight of the cartridge case can be effected.

More particularly, when conventional propellant grains are loaded into a cartridge only about 60% of the space between the closed end of the cartridge or shell in the projectile contains propellant and the remaining 40% constitutes voids. It will be evident accordingly that by increasing the density of the propellant without sacrificing desirable burning rates, the advantages of smaller sized cartridges for a given weight of propellant can be realized. In addition, with presently available propellants the burning rate is such that the peak pressure behind the projectile does not occur until the projectile has moved some distance down the barrel. Moreover, this peak pressure behind the projectile is not sustained for any appreciable length of time. Evidently, when the peak pressure is reached, the propellant remaining burns at a rate which is insufficient to maintain the peak pressure behind the rapidly accelerating projectile. This is ineflicient because propellant gas is most effectively utilized when peak pressure is maintained within a minimum of volume behind the projectile. A short time after peak pressure has been achieved, the propellant is totally consumed and during the remainder of the projectile travel, the gas is expanding adiabatically.

The foregoing is a result of the accelerated movement of the projectile down the barrel of the firearm Which leaves a volume behind it increasing as a function of time squared. As an approximation, the pressure generated by the burning propellant increases more or less as a direct function of time although the rate of increase is large at first and falls oil as the volume behind the projectile increases. Thus, the pressure exerted on the projectile is not uniform but gradually increases towards its peak value as the projectile moves. If the peak pressure of the generated gas behind the projectile could be achieved prior to any appreciable movement of the projectile and this peak pressure maintained for a given period of time corresponding substantially to the time required for the complete burning of the propellant, a far greater efficiency in projecting the projectile from the firearm would result. In other words, a given muzzle velocity of the projectile could be realized with less propellant burning in the manner as described than would be the case with propellant which does not provide a peak pressure until after movement of the projectile has taken place over a substantial distance.

With all of the foregoing in mind, it is accordingly a primary object of the present invention to provide a novel propellant, including the advantages set forth in my referred to copending application, and also enabling a given projectile energy to be realized with less propellant than is normally required for realizing such energy. Alternatively, increased projectile energy can be realized for the same amount of propellant that would normally result in a lesser projectile energy. The practical result is, that cartridges or shells may be made smaller with less propellant for a given projectile energy than has been possible heretofore.

Briefly, this object is realized by providing a firearm propellant design such that the space between the closed end of the shell and the projectile is substantially filled so that voids occupy no more than 25% of this space. The propellant itself includes a burning inhibitor defining ignition lines such that a substantially peak propellant pressure is applied to the projectile prior to any appreciable movement of the projectile and is maintained during the time period required for the propellant to be completely burned. This is accomplished by establishing a burning pattern in which gas is generated at :a rate proportional to time square-d. Since this also matches the volume generated behind the constantly accelerating projectile, peak pressure is maintained throughout burning with the result that maximum energy is imparted to the projectile for a given amount of propellant. It is understood that the burning rate and quantity of propellant must be matched to the weight of the projectile in order to achieve the required level of pressure. Achieving this quantitative balance is an engineering task.

A better understanding of the invention will be had by referring to a preferred embodiment thereof as described in conjunction with the attached drawings, in which:

FIGURE 1 is an exploded perspective view of a shell, the novel propellant of this invention, and a projectile;

FIGURE 2 is a cross-section of the propellant taken in the direction of the arrows 2-2 of FIGURE 1;

FIGURE 3 is a fragmentary cross-section taken in the direction of the arrows 33 of FIGURE 2;

FIGURE 4 is a pressure diagram illustrating certain relationships during the firing of a projectile with conventional propellant material; and

FIGURE 5 is a pressure diagram similar to FIGURE 4 useful in explaining the advantages of the propellant of the present invention.

Referring first to FIGURE 1 there is shown a cartridge or shell 10 and associated projectile 11. Also illustrated is the novel propellant of this invention indicated generally by the numeral 12. As shown, this propellant comprises a charge made up of a plurality of discs, one of which is separated and illustrated at 12'. These discs are stacked to define a cylindrical shape oriented such that the longitudinal axis of the cylindrical shape corresponds with the longitudinal axis of the shell 10.

Each of the discs includes a central opening 13 such that when the discs are stacked as shown, a longitudinal bore is defined through the cylindrical shape. In addition, the exterior of the cylindrical shape includes longitudinally extending recesses such as indicated at 14 and 15. The purpose for these recesses will become clearer as the description proceeds.

Referring now to FIGURES 2 and 3, details of one of the discs making up the propellant charge of FIGURE 1 will be understood. As shown in FIGURE 2, the longitudinal recesses are circumferentially spaced about the exterior of the cylindrical shape, additional such recesses being shown at 16 and 17. These recesses define small voids with the interior cylindrical wall of the shell 10. The face of the disc has portions covered with an inhibitor 18, other portions being free of the inhibitor to define ignition lines 19.

With particular reference to FIGURE 3, the inhibitor 18 is illustrated as heavily cross-sectioned, the portions of the surface of the disc 12 not covered by the inhibitor defining, as mentioned, the ignition lines 19. It will be noted that the opposite face of the disc also includes an inhibitor 20 defining ignition lines 21 which are staggered with respect to the lines 19.

When the discs are stacked, the granular nature of the charge material itself will tend to hold the discs from completely tight face to face engagement -with each other so that there will be small spaces between the discs for receiving hot gases. In this respect, the propellant as -described in FIGURES 1, 2 and 3 is initially ignited along the central bore 13 by the primer. The hot gases pass radially from the central bore 13 up between the discs to the outer surface of the cylindrical configuration and to the longitudinal recessed portions such as indicated at 14, 15, 16 and 17. All of the various ignition lines are thus subject to hot gas and are all ignited substantially simultaneously.

The manner in which each of the discs progressively burns is illustrated in FIGURE 3. For example, at a time T the burning commences outwardly in a semicylindrical pattern with uniformly increasing radius. This increase in radius is indicated at the times T T T and T in FIG- URE 3. It will be understood that all of the ignition lines are fired substantially simultaneously so that actually the various radii illustrated in FIGURE 3 for the successive ignition lines are as they would appear at spaced time intervals.

It will be evident from FIGURE 3 that a semicylindrical burning pattern takes place with each ignition line constituting the axis of the semicylinder. Further, it will be evident that the radius of the semicylinder increases substantially uniformly with time or is directly proportional to time. As a result, the actual area, which is proportional to the radius squared, and thus the volume of the semicylindrical shape, since the length of each ignition line is constant, is burned at a rate proportional to times quared, assuming a constant chamber pressure. Therefore, the resulting generated gas volume increases as time squared.

By staggering the positions of the ignition lines on opposite sides of each face of the discs, the foregoing burning pattern can be maintained until substantially the entire charge is consumed.

Referring now to FIGURES 4 and 5, the operation of the propellant will be better understood. In FIGURE 4, there is illustrated :by the curve 22 the relationship of pressure in the volume between the closed end of a shell and a projectile traveling down the barrel of a firearm when propelled by a conventional propellant change. The abscissa of the curve in FIGURE 4 represents the distance traveled by the projectile. Since the projectile is accelerated, the distance traveled is proportional to the product of average acceleration and time squared.

As indicated 'by the initial portion 23 of the curve 22, the pressure builds up such that the peak pressure is not achieved until the projectile has traveled a distance indicated at the vertical dash line D. Thereafter, the remainder of the propellant burns a a gradually reducing pressure until it is totally consumed and the generated gas simply expands adiabatica'lly as the projectile continues down the barrel. Thus, the energy or work done by the scribed in FIGURES 1, 2, 3 in the present invention is used. In FIGURE 5, there is illustrated a pressure curve 25 wherein the initial portion of the curve as indicated at 26 defines a substantially constant pressure corresponding to the peak pressure attained by the propellant of FIG- URE 4. Thus, it will be clear that the pressure builds up to maximum or peak pressure takes place extremely rapidly and then the charge burns in the manner described in FIGURE 3 to generate gas at a rate proportional to time squared.

' It will be clear from FIGURE 5 that the distance traveled by the projectile at the time the pressure reaches its maximum level at 26 is negligible. At the distance D, the propellant is completely burned and the gas then expands adiabatically as indicated by the fall off portion of the pressure curve at 27.

It will be clear from FIGURE 5 that the energy provided by the propellant of the present invention, as indicated by the area A2 under the curve 25, is considerably more than the energy as indicated by the area A1 of FIGURE 4. Further, it will be clear from FIGURE 5 that a major advantage of the present invention is the ability to reach the limiting combustion pressure rapidly and to sustain combustion at that level until substantially all of the propellant is consumed. This characteristic of precise combustion rate control may be employed to impart higher velocities to projectiles than is possible in present practice since peak pressure can be sustained over an appreciably longer period of time.

If greater projectile velocity is not an objective then the present invention could be employed to provide normal projectile velocities with a smaller amount of propellant due to the rapid rate of pressure buildup indicated in FIGURE 5. This is due to the great reduction of cartridge case void volume which must be filled with high pressure gas and to the expeditious and positive method of achieving propellant ignition.

From the foregoing description, it will thus be evident that the present invention has provided a greatly improved propellant wherein not only is relatively dense packing of the propellant possible enabling smaller shells to be formed for a given amount of propellant but in addition the propellant is so designed that its burning rate at constant pressure, is proportional to time squared thus providing the possibility of greater projectile velocity if the designer so requires. In addition, the rapid and precise method of ignition improves efiiciency of energy transfer to the projectile and this reduces the amount of propellant required for a given level of firearm performance.

What is claimed is:

1. A progressive burning firearm propellant for use in a firearm shell comprising: a charge shaped to fill substantially the space between the closed end of said shell and a projectile such that voids in said space and charge constitute less than 25% of the entire volume of said space, said charge being made up of a plurality of discs in a stacked coaxial configuration to define a cylindrical shape with the axis of said cylindrical shape coaxial with the longitudinal axis of said shell, each of said discs having a central opening to define a longitudinal bore through said charge coaxial with said longitudinal axis of said shell; and a burning inhibitor covering portions of at least one of the faces of each disc in a pattern to leave other portions free of said inhibitor, said other portions defining ignition lines so arranged that burning of said charge upon initial ignition along said ignition lines generates propellant gas at a rate proportional to time squared, the exterior surface of said cylindrical shape defined by said discs including recesses to define voids between said cylindrical shape and the inside cylindrical wall of said shell whereby ignition of said charge through said longitudinal bore ignites said ignition lines by hot gases passing radially from said bore between said discs to the outer surface of said cylindrical shape and to the 5 References Cited UNITED STATES PATENTS 1,906,675 5/1933 Wagner l02-l04 3,017,744 l/l962 Jett 6035.6 3,069,844 12/1962 Bearer 6035.6

FOREIGN PATENTS 5,927 1915 Great Britain. 85,530 3/1955 Norway.

OTHER REFERENCES Cartridges of the World, by Frank C. Barnes; Apr. 9, 1965. Pp. 308-312 req.

15 ROBERT F. STAHL, Primary Examiner. 

